Detailed notes on carbs

Question 1

What are carbohydrates?

Answer 1

• Carbs are basically made up of C, H and O (term comes from carbon= C and Hydrates= water)
• Occur primarily in plants
• Found in lactose and glycogen (meat)
• Photosynthesis produces carbs (energy)

Question 2

Classification of carbohydrates based on?

Answer 2

• Saccharide units
• Saccharide units and health
• Glycemic index

Question 3

Classification based on saccharide units?

Answer 3

Related to the size of the molecules in simple and complex sugars

Question 4

Classification based on saccharide units and health?

Answer 4

Shown in the table. they are broadly classified as

• simple carbs: Monosaccharides and disaccharides
• Complex carbs: Starches and dietary fibre

In addition the digestibility is also indicated in the table (see other notes for table)

Question 5

Glycemic index

Answer 5

Is based on how rapidly the carbs are taken up into the bloodstream. Is an index used to rank foods according to their different behaviour in our bodies - blood glucose levels.

Another definition is:
- A measure of how fast and how far blood sugar raised after you eat a food that contains carbs.

Question 6

Key factors tat determine the glycemic index of a food?

Answer 6

• Fiber content
• Type of starch
• Physical form
• Ripeness

Question 7

How fiber effect GI?

Answer 7

• Is the amount of relatively indigestible polysaccharides (cell wall)
• This determines the speed at which digestive enzymes attack the starch carbs and therefore the release of sugar molecules into the bloodstream

Question 8

How type of starch effect Gi?

Answer 8

Eg. Boiled rwhich rice appears easier to break into sugar molecules than boiled potato

Question 9

How Physical form of carb effects GI?

Answer 9

Finely ground grains are easier to digest then coarsely ground grains

Question 10

How ripeness of carb effects GI?

Answer 10

Particularly relates to fruit. Ripe ones are sweeter and have more sugar and higher GI than unripe

Question 11

Properties of carbs

Answer 11

• Solubility
• Crystallization
• Colligative properties
• Sweetness
• Colour
• Humactancy’hygroscopicity
• Viscosity

Question 12

carb solubility

Answer 12

Surgars vary in solubility.
Decreasing order:
- Fructose
- Surcose
- Glucose
- Maltose
- Lactose

Question 13

Crystallisation

Answer 13

The concentration and temp for cooking sugar solutions is determined whether to solution is:

• Unsaturated
• Saturated
• Supersaturated

Question 14

Unsaturated solution>

Answer 14

Does not contain all the dissolved solute that the solvent can hold.

Eg. 10g of sugar in 100ml of water will give us an unsaturated solution,

Question 15

Saturated solution?

Answer 15

Contains all the dissolved solute that the solvent can hold at a definite temperature.

Eg. 203.9g of sugar to 100ml water at 20 degrees will give us a saturated solution

Question 16

Supersaturated solution?

Answer 16

Contains more solute than the solvent can hold @ a particular temp.

Eg. 487.2 g of sugar in 100ml water at 100 degrees is a saturated solution. If the solution in allowed to cool to 20 degrees the solution would have contained more sugar than the water can hold.

Note! this excess beyond saturation remains in solution as the temperature drops until crystallisation is initiated by treatmeants including stirring or adding crystals

Question 17

Factors effecting crystal growth and size? (saturated)

Answer 17

• Temperature
• rate of cooling
• amount of seeding at the metastable region
• agitation
• purity of raw material

Question 18

Carb colour

Answer 18

Only carbs that are reducing sugars are able to react with amino groups to form a brown and flavoursome colour.

The reaction forming this brown colour is called “maillard reaction”or carboxyl-amine browning.

This means that for sucrose to participate in the ration between the conbonyl group of reducing guards and the free amino groups of protein, is has to be cleaved (split/cut) at the alpha 1-4 linkage.
This gives us glucose and fructose which are reducing sugars and therefore these can then participate in the Maillard reaction.

Question 19

Hydrolisis

Answer 19

Hydrolysis is the breakdown of a complex substance to a simple substance by chemical reaction with water molecules. The word “hydro” refers to water and “lysis” refers to breakdown.
Components of food including carbohydrates, proteins and lipids do undergo hydrolysis and these reactions are accelerates by certain factors including acid, heat or enzymes.